Antarctic Melting
Posted by Stuart Staniford on March 3, 2006 - 1:44pm
Just a quick note. There is a new paper by Velicogna and Wahr in Science today (you have to pay) which attempts to assess the overall mass balance of Antarctic ice by satellite measurements of the earth's gravity field.
Using measurements of time-variable gravity from the Gravity Recovery and Climate Experiment (GRACE) satellites we determine mass variations of the Antarctic ice sheet during 2002-2005. We find that the ice sheet mass decreased significantly, at a rate of 152 ± 80 km3/year of ice, equivalent to 0.4 ± 0.2 mm/year of global sea level rise. Most of this mass loss came from the West Antarctic Ice Sheet.
There are several cautions here. That ± 0.2mm is a 1 sigma error bar, so this is only a two-sigma result. Furthermore, it's a short time period, so we don't know how this fits into an overall trend. Finally, it's a new method, so if the referees missed a methodological problem, that will show up in time. In particular, the ice mass loss signal emerges as an offset to a sizeable correction due to post ice-age rebound which has to be estimated from ice history models. That sounds a little scary to me - I'd feel better seeing this replicated with other independent analyses.
All that said, it's certainly not in the good news column. If this result holds up, it suggests that Greenland and WAIS are contributing roughly equally to sea level rise at present.
We discussed sea level rise before in
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—Moiseide Ostrogorski (1902, 302-303)
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Bob Shaw in Phx,AZ Are Humans Smarter than Yeast?
"The Bentley Subglacial Trench is a vast trench in Antarctica. At 2,555 meters (8,326 ft) below sea level, it is the lowest point on the surface of the earth not covered by ocean, although it is covered by ice. It is similar in size to the nation of Mexico. [This is huge! Even if it was not covered by ice, a human could not go down to the very bottom because the vastly increased air pressure would overcome your lungs diaphramic muscle ability to exhale; you would need a deep sea diver's pressure suit to explore this area"
I get confused. Anglogold's Western Deep Levels in South Africa is the world's deepest mine at 12300 ft.I think, and as far as I know no pressure suits are required to work at its lowest levels...
I think this trench is cut off from the ocean. It is hard to tell, I could not find any maps that clearly show the topology of the Antarctic land under the ice, but if the ice were gone, the ocean would probably not rush into the Bentley, so it would stay dry. So if a volcanoe were to melt ice there, it should not destabilize anything, just make a lake. There would be no lubricated glaciers quickly sliding off of the Antarctic.
I did find this:
http://usarc.usgs.gov/ant-ogc-viewer/viewer.htm
Thxs for responding. Yeah, on second thought, I agree with you that I blew the pressure assumption. If the caldera was as big as Yellowstone, or similar to previous Antarctic calderas [even bigger than Yellowstone], this could potentially be filling in the trench displacing all that water. But the big problem would be from the predicted 1500 ft or more of uplift from earthquakes, other volcanoes spouting off, and ejecta melting the main Antarctic ice sheet. The Western Antarctic Ice Sheet [WAIS] is only good for 20ft of sea-level rise-- the other ice sheet is good for 190 ft-- REAL BIG PROBLEMS for us.
My tutorial was highly speculative-- I bet most real scientists would laugh at the whole shebang sliding off in a short twenty year timeframe-- A 1,000 year gradual process is probably much more likely. But who knows, Nature can be very surprising.
Bob Shaw in Phx,AZ Are Humans Smarter than Yeast?
On the plus side, this ice will become a lake that will not empty into the sea.
Bob Shaw in Phx,AZ Are Humans Smarter than Yeast?
(I'm encouraging you...I like what you did. It just was a blogpost (if not a book), not a comment! That's all!)
Help, I am confused. I posted a variation of this same post on the forum Yahoo:AlasBabylon with no problem #24085. The moderator, the Great Scott, had no problem with its length, and he too was impressed with its content. It is free for anybody to read if they join [also free], but I cannot make an autolink to it. Other AB posters have included different articles that are much, much longer than mine-- no problem. Is there a technical difference in equipment & software between these forums, or just a different social norm of netiquette culture? Sometimes I feel like a stranger in a strange land on TOD, help me conform. :] Sorry to make you have to do that work, but I thought I would save everybody the gobs of research that I did.
I just never thought I needed a personal blog as long as my articles are available in the AB archives. I have got hundreds of them. I have even seen some of my postings reposted on Italian websites and plagiarized elsewhere.
Clue me in, if you can.
Bob Shaw in Phx,AZ-->DUMBER THAN YEAST!
What I would suggest on these kinds of topics is, in the comments, post an executive summary that interests people, then link that material you want them to read posted elsewhere (again, perhaps on your blog that you're going to set up today for free over on blogger (because you should!), because work like yours is really good, and should be out there influencing the discourse!) You could post your best work on your blog that way, and then it's outside of the AB archives so that others can hear your ideas.
Again, this is one of those "unwritten rules"...it's just that one commenter running the comments usually just pisses people off, then we get emails in the TOD inbox (as we did today), then I have to do something like this. :)
Okey-Dokey, I will flail away at creating a blog after doing some more lurking first. See-ya Gang!
Bob Shaw in Phx,AZ Are Humans Smarter than Yeast?
You talked about posting links and here is a
good one about snow and ice and guess what?
It's free. www.nsidc.colorado.edu/
enjoy.:)
There are many sites that offer free Web space or blogs. If you post your articles to your own Web site or blog, you can post links to them. Much better than dumping War and Peace in the middle of thread here, or forcing people to join a Yahoogroup. (Many people will not sign up with Yahoo anyway, due to their privacy policy.)
Personally, I like OurMedia.org. It offers not only blogging, but file upload for text, audio, video, and image files. It's a bit slow to upload sometimes, but download is usually fine. And it allows remote linking.
I learned may things from your post, and now am a whole lot smarter about Antarctica. Quite a wierd place - almost sounds like another planet! It's hard to picture a temperature of -129 degrees F along with hurricane-force winds. Due to its shear size, it sure seems like Antarctica has the potential for affecting a lot of things 'up here'.
Why was it 'bad'? It was great content. Compelling. Perhaps totally wrong and other events (say a global themonuclear war or the sun becoming a red giant) would render the eventual removal of ice and water level a non-issue.
Why not copy it and make it a topic for discussion all by itself as its own bad self. Natural disasters/crop failures/et la are now made less painful because of the release of the energy of stored sunlight. The 'worse case' outlined in that post would effect some nations by removing them from the globe, and other nations would have to have 1/2 of their population move. A bigger issue would be the placing underewater of all that costal buildings and production capacity. So there IS a peak oil tie to such an event.
Oh! And maybe my grandchildren (if I ever make the breeding) could pick up bananas in Moscow. No matter, there won't be enough oil to transport them from Ecuador.
I heard somewhere, there are deep-water oil fields near Antarctic coast but no international agreement on the rights below latitude 60. ???
Hey, Amory Lovins grows bananas in Colorado.
The real problem is that the erosion of these glaciers is occurring on a much faster rate than was anticipated by prior modelling.
OK, I stand by what I said. Plausible PGR contributions? Since when has the Antarctic been subject to geological uplift in the many thousands of years since the last Glacial Maximum? -- not to mention perhaps 35 millions before that? And these results should not be "averaged over all Antarctica". What's happening in West Antarctica and what's what's happening in the Eastern Antarctica big ice sheet don't necessarily correlate at all and why would we expect that? The geology and climate considerations are completely different. Maybe it will snow more in East Antarctica and erosion in West Antarctica won't surpass that, so the ice sheets in these two regions will remain "in balance". That would make the "averaging approach valid" I suppose. As for calculating all this, that is being worked out but I haven't see any significant evidence that accelerating erosion contributing to global sea level rise from West Antarctica is being compensating by an increase in ice cover in East Antarctica.
Thanks for the quote from this Science article I haven't seen.
best, Dave
I'd also imagine if ocean rise must now to be attributed to Antarctica (as many media reports of this story are simply stating as fact), that would imply ocean rise due to all other factors elsewhere must be less than previously thought - since the data is not that "oceans are rising faster" than expected but that the West Antarctica area is unexpectedly losing mass.
Might this not be the kind of Rorschach-staring science Michael Crichton - curse his soul - was pointing at?
You can say what you like about Chrichton, but he did his homework. Also, in the more than 800 reader reviews of STATE OF FEAR, I noted that those who seemed to have the best scientific credentials often gave the book five stars, while those who hated it were often typical chattering-class pundits who never got beyond seventh-grade algebra.
Click to enlarge
Breathe now, while it's easy. No, I'm confused, move inland -- this is a water thread, not an air thread.
The earth is spherical object spinning about an axis. It has a certain distribution of mass and hence a certain moment of inertia about its axis of rotation.
Now, If I remove a certain amount of mass (ice) from the polar regions, where the radius from the earth's surface to the axis of rotation is relatively short, and redistribute that mass further out toward equator, where the radius is much greater, will I not have increased the overall moment of inertia of the earth?
And by doing so, will not the rotational speed of the earth decrease by some slight amount, in the same way that a figure skater slows down by extending her arms?
Has anybody calculated the magnitude of this sort of effect? What about wobble?
The Anomaly In The Earth's Wobble Continues
The Polar Motion Anomaly of 2005/2006
More:
http://www.michaelmandeville.com/earthmonitor/polarmotion/2006_wobble_anomaly.htm
I didn't read all of itl yet, but from what I skimmed, it looks like pretty heavy stuff.
I can see now that there are a great many factors affecting the rotation of the earth. I had completely forgotten about the effect of the moon causing a periodic bulging. Then you have tectonic plates doing their thing, and molten gooey stuff sliding around inside. I guess that from the standpoint of spin dynamics, the earth is more like a giant water balloon filled with viscous material that is continually slipping and sliding and being pushed and pulled by outside forces (the moon).
So far from what I read of the article, I didn't see any mention of the possible effect of polar ice caps melting.
I come at this from a background in digital mapping of the earth's surface, both dry land and water covered land. The changes that occur to maps over a set perios of time causes great head aches to those that have to keep up with it all.
The company that maps the US southern coast is likely 3 year behind in updating total data sets, just because of last 2 seasons of hurricanes, Not to mention ice melt too.
Fun Fun Fun for some guys, I am glad I went into full time Writing and Koi breeding and Am moving further inland.
Any One in Colorado give me a heads up.
Charles.
There's an example of the kind of thing he does here.
It is both literal (arctic ice melting) and highly evocative (nuclear reactor meltdown or total collapse of a system).
It certainly would get much more attention that 'global warming', a term that I think many people are bored with because they associate it with those pesky whiny environmental greenies.
I agree with you that stories and words, anecdotes and emotions are necessary for communicating the truth to the public effectively. However, they are almost useless for determing what the truth actually is (at least about any large scale phenomenon) - for that one typically needs graphs and numbers and statistics.
You have touched on one of the Very Most Fundamental (VMF) questions: What is truth? What is the nature of truth? How can we know it when we find it? Or, in other words, what is the nature of knowledge?
Plato believed that mathematical truth was the deepest truth, that to understand and know and explain the universe one had to first get at the underlying mathematics. Recall the Alegory of the Cave--most of us think we have notions of the truth, but all we really see is flickering shadows.
Aristotle, on the other hand, believed that there was an empirical reality more fundamental than mathematics. He was first and foremost a marine biology student, and he had been educated by his physician father in empirical methods. (e.g. Keep King Philip alive and healthy, or you die.) Plato started out as a poet, and I have noticed an affinity between poets and theoretical physicists: Both of them aim ruthlessly to eliminate the nonessential and get at the meat of the matter.
It has been said that all of us are either Platonists or Aristotelians, and there is something to that. Clearly, Stuart, you are an Aristotelian (a scientist), and though I love Plato, at heart I too am an Aristotelian.
Math describes reality.
Math itself is a language, a form of logic, a powerful way to deal with reality--but in my opinion is at bottom a tool to understand "reality" rather than the "reality" itself.
These are deep empistemological and metaphysical waters, however--far too deep for drilling:)